There is a growing interest in embedding nano-metals in polymer matrices because of antimicrobial and conductivity properties (thermal and electrical). By combining the properties from both inorganic (i.e., silver, gold, copper etc.) and organic (polymer) systems, new composite products can be generated that find expanded use in antimicrobial applications, thermal and electrical conductivity applications, and so on.
Metals have been used in medical care to prevent and to treat infection. In recent years, that technology has been applied to consumer products to prevent transmission of infectious disease and to kill harmful bacteria, such as, Staphylococcus and Salmonella. In common practice, noble metals, metal ions, metal salts or compounds containing metal ions having antimicrobial properties can be applied to surfaces to impart an antimicrobial property to the surface. If, or when, the surface is inoculated with harmful microbes, the antimicrobial metal ions or metal comp exes, in effective concentration, slow or prevent growth of those microbes.
In the context of antimicrobial coatings, colloidal silver has been indicated to work as a catalyst disabling a metabolic enzyme that bacteria, fungi and viruses have. Many pathogens can be eradicated effectively in the presence of even minute traces of silver. Indeed, colloidal silver is effective against more than 650 different pathogens. Unlike antibiotics, strains resistant to silver have yet to be identified.
Another area of interest is the use of composite resins in products that utilize the thermal and/or electrical conductivity properties of the metals. Those include, inks, toners, biosensor materials, composite fibers, cryogenic, superconducting materials, cosmetic products, and electronic components. Methods, such as, 3D printing and ink jet deposition, can be used to manipulate the functional composite resins to form a substrate or device of choice.
Conventional methods for making polymer/metal nanostructured materials require melt mixing or extrusion of metal nanoparticles with polymer matrixes which often leads to aggregated metal particles, as reported in the literature (also called ex situ).
New methods are emerging slowly that use in situ synthesis of metal nanoparticles in polymer matrices which involves the dissolution and reduction of metal salts on matrices or simultaneous incorporation during polymer synthesis. The polymer matrix has a role in keeping the metal nanoparticles dispersed as well as maintaining overall chemical and mechanical stability. WO 2013026961 describes a process for obtaining an ionomer, such as, an antimicrobial amorphous ionomer composition wherein at least one amine functional polymer is reacted with a silver halide. The metal is incorporated into the polymer after formation of the polymer, not during polymer formation.
There remains a need for new methods and composite binder resins wherein metal ion is incorporated within the polymer backbone during synthesis. Ionomer composite resins and core/shell nanoparticles thereof, wherein metal ion (meth)acrylate monomers are polymerized with styrene/monomers to form the resins, are described.